Lamp ballast and method of producing same

ABSTRACT

A lamp ballast wherein a magnetic core and coil assembly is encased within a housing and is spaced from the housing with a suitable filler material filling the space between the magnetic core and coil assembly and the housing. The magnetic core and coil assembly is suspended within the housing having an open top, being spaced from the sides and bottom thereof by suspension means. The housing or casing is then partially filled with the suitable filler material in liquid form, to a level wherein at least a portion of the magnetic core and coil assembly is immersed in the filler material. After the filler material has hardened to an extent that it will support the core and coil assembly, portions of the suspension means are removed such that when the housing is completely filled with the filler material the core and coil assembly will be completely surrounded by the filler material and the suspension means will not extend from the core and coil assembly to the casing. Thus, the suspension means does not provide a surface joining the casing and the core and coil assembly along which moisture entering the casing may reach the core and coil assembly.

United States Patent [151 3,655,906 Apr. 11, 1972 Robb [54] LAMP BALLAST AND METHOD OF PRODUCING SAME [72] lnventor: Robert E. Robb, Danville, ill.

[ 73] Assignee: General Electric Company [22] Filed: Oct. 19, 1970 [21] Appl. No.2 81,759

[52] US. Cl ..l74/52 PE, l74/DlG. 2, 264/278 [51] Int. Cl. ..H05k 5/06 [58] Field of Search ..l74/DlG. 2, 52 PE; 336/96,

[56] References Cited UNITED STATES PATENTS 3,173,059 3/1965 Stake ..336/96 ux [57] ABSTRACT A lamp ballast wherein a magnetic core and coil assembly is encased within a housing and is spaced from the housing with a suitable filler material filling the space between the magnetic core and coil assembly and the housing. The magnetic core and coil assembly is suspended within the housing having an open top, being spaced from the sides and bottom thereof by suspension means. The housing or casing is then partially filled with the suitable filler material in liquid form, to a level wherein at least a portion of the magnetic core and coil assembly is immersed in the filler material. After the filler material has hardened to an extent that it will support the core and coil assembly, portions of the suspension means are removed such that when the housing is completely filled with the tiller material the core and coil assembly will be completely surrounded by the tiller material and the suspension means will not extend from the core and coil assembly to the casing. Thus, the suspension means does not provide a surface joining the casing and the core and coil assembly along which moisture entering the casing may reach the core and coil assembly.

4 Claims, 7 Drawing Figures as 68 24 72 I lid? 7 /7 7" 5/7 sf a $2 m w s6 7 22 54 t I L4 I I 1' 75 Patented April 11, 1972 2 Sheets-Sheet 1 Pober't E. Robb,

The present invention relates to an electric discharge lamp ballast, and particularly to a fluorescent lamp ballast having improved moisture resistance. One factor that reduces the life of fluorescent lamp ballasts, particularly in applications where the ballast is exposed to a wide range of conditions, such as humid and corrosive atmospheres and relatively high and low temperature environments as may be encountered in various extremes of weather, is the entrance of moisture through the case to the core and coil assembly. The entrance of moisture into the core and coil assembly and particularly into the coil may cause an electrical failure of the coil. Any member, regardless of whether it is formed of a metallic or insulating material, which extends between the core and coil assembly and the housing may potentially provide a path for the entrance of moisture into the core and coil assembly. Moisture may enter the core and coil assembly in the presence of two conditions, the presence of a path for the entrance of moisture into the casing in a region where a member extending from the core and coil assembly contacts the housing, and the presence of a path for moisture flow along the member extending between the case and the core and coil assembly. The later path may for instance be provided along the surface of a member extending between the case and the core and coil assembly when there is not complete and continuous adhesion between the member and the filler material. In the absence of complete adhesion, a continuous void may be provided along the surface of the member between the housing and the core and coil assembly, through which moisture may pass from the housing to the core and coil assembly. The entrance of moisture into the coil may cause a degradation of the insulating material of the coil and an'eventual failure of the coil and therefore of the magnetic core and coil assembly.

OBJECTS OF THE INVENTION It is therefore a primary object of this invention to provide a novel and improved lamp ballast having increased resistance to the entrance of moisture to the core and coil assembly of the lamp ballast, and a method of producing such a lamp ballast.

'It is another object of the present invention to provide a novel and improved lamp ballast and method of producing the same which minimizes the possibility of the entry of moisture into the core and coil assembly, particularly when the lamp ballast is exposed to a wide range of conditions, such as relatively high humidity and relatively high and low temperature variations as may be encountered in various extremes of the weather in outdoor applications.

It is a further object of this invention to provide a novel and improved lamp ballast and method of producing the same which incorporates a minimum number of inexpensive parts which are readily assembled with minimal effort and skill.

SUMMARY OF THE INVENTION The foregoing objects are accomplished in accordance with this invention when in a preferred embodiment a magnetic core and coil assembly is placed within a housing and supported therein out of contact with the housing by temporary suspension means. The magnetic core and coil assembly, and other electrical components making up the lamp ballast, are positioned within the housing with the leads for making external connections to the coils and other electrical components extending from the housing through one or more apertures in the housing which are provided with insulating and sealing grommets. The temporary suspension means suspends the magnetic core and coil assembly within the housing in a spaced relationship with respect to both the side walls and the base of the housing. The housing is then partially filled with suitable filler material in liquid form to a level wherein upon solidification the filler material will support the magnetic core and coil assembly within the housing. At least those portions of the temporary suspension means which engage or extend without the housing are then removed. thereafter the housing is completely filled with the tiller material so as to completely surround the magnetic core and coil assembly. The assembly of the lamp ballast is thereafter completed by applying a cover to the housing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a top plan view of a preferred embodiment of the novel and improved lamp ballast of this invention in a first step of construction.

FIG. 2 shows an elevation view of the novel and improved lamp ballast in a longitudinal section taken along the line 22 in FIG. 1, but at a second step of construction.

FIG. 3 is an elevation view of the lamp ballast in transverse section taken along the line 3--3 in FIG. 1.

FIG. 4 is an elevation view of the lamp ballast in transverse section taken along the line 44 in FIG. 2.

FIG. 5 is an elevation view of the completed lamp ballast.

FIG. 6 is an elevation view of the lamp ballast in transverse section taken along the line 6--6 in FIG. 5.

FIG. 7 is a perspective view of a preferred form of the temporary core and coil assembly suspension means.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGS. 1 and 2 the novel and improved lamp ballast l0 and method of producing the same will be described. The lamp ballast 10 is contained within a suitable housing which is shown as a metallic casing I2. The casing 12 is formed with a base 14, upstanding sidewalls I6 and I8 and end walls 20 and 22. As shown in the preferred embodiment of this invention, the electrical components of the lamp ballast include a core and coil assembly 24 and a capacitor 26. However, in ballasts for different types of electric discharge lamps and for different numbers of electric discharge lamps other components such as additional capacitors and additional core and coil assemblies may be included within the housing.

The electromagnetic core and coil assembly includes a shell-type core 28, preferably formed of a plurality of layers of laminations 30. The layer of laminations are made up of punchings which form a pair of outer legs 32 and 34 and a central leg 36 shown by the dash line in FIG. 1. Window openings 38 and 40 are formed between the central leg 36 and the outer legs 32 and 34 of the core 28. A pair of winding or coil assemblies 42 and 44 are mounted on the central leg 36 and occupy most of the space in the windows 38 and 40. When the shelltype core formed of laminations 30 is assembled with the coil assemblies 42 and 44, the complete assembly is held together by a pair of end clamps 46.

Electrical connections between the coil assemblies 42 and 44 and the capacitor 26 are made through a pair of terminal boards 48 and 50 supported from the end clamps 46. Terminals 52 are secured to insulating boards 54 in some manner, such as by staking, and the insulating boards 54 are secured to the end clamps 46 such as by tabs 56 provided on the end clamps. While not shown in the figures, the leads extending from the coil assemblies 42 and 44 are soldered or otherwise electrically connected to the appropriate terminals 52. Appropriate electrical interconnections between the capacitor terminals 58 and the coil assemblies 42 and 44 are made by insulated leads 60 extending between the capacitor terminals 58 and appropriate terminals 52.

External electrical connections to the core and coil assembly and the capacitor 26 are made by way of insulated leads 62 which extend through apertures in the end walls 20 and 22 of the housing. Grommets 66 are provided in these apertures to further insulate the insulated leads 62 from the end walls 20 and 22, and to assure that the apertures are substantially closed so as to prevent the outflow of the liquid filling material.

In order to insure that the insulated leads 60 and 62 interconnecting the coil assemblies and the capacitor and extending external of the lamp ballast do not contact the walls or the top-of the housing, a pair'of resilient loops such as rubber bands 67 are placed over the insulated conductors and the core and coil assembly 24 and the capacitor 26 to hold the insulating leads close thereto.

In constructing or assembling a ballast in accordance with the method of this invention, a temporary suspension means comprising a pair of U-shaped support members 68 are placed around the end clamps 46 with the bight portion 70 extending beneath the clamp as viewed in FIG. 2 and the leg portions 72 extending along the side portion of the clamp as viewed in FIG. 2. The free ends of the leg portions 72 are provided with outwardly extending hooks 74 which engage the upper edges of the side walls 16 and 18 of the housing as the core and coil assembly 24 is lowered into the housing 12. The preferred support member as shown in FIG. 7 is formed of a cylindrical, fairly rigid, steel wire which is formed in a general U-shaped with a bight portion 70, leg portions 72, and outwardly extending hooks 74 formed at the free ends of the legs 72.

Referring to FIGS. 1 and 3, it will be observed that the core and coil assembly 24 as suspended within the housing 12 by the support members 68 is spaced from the side walls 16 and 18, from the end walls 20 and 22 and from the base 14. Thus, no portion of the core and coil assembly is in contact with the housing 12.

As the core and coil assembly is placed within the housing 12 and suspended therein by the support members 68, the capacitor 26 is also placed within the casing. An insulating film 76 is wrapped around the capacitor 26 to further insulate the capacitor should moisture in any way enter the housing 12. In the preferred form of this invention, the capacitor 26 would be supported by its leads and the resilient loop or rubberband- 26 and would not contact any portion of the housing 12. After the core and coil assembly 24 and the capacitor 26 are placed in the housing 12, the insulating leads 62 are threaded through the grommets 66 to extend through the end walls 20 and 22 of the housing.

With the electrical components of the lamp ballast thus assembled and supported within the housing 12, the housing is partially filled with a suitable filler 78, such as an asphalt compound that is both electrical insulating and heat conducting.

Due to the spacing of the core and coil assembly 24 and the capacitor 26 from the side walls, end walls and base of the housing 12, to the extent that the housing 12 is filled with the filler material 78, as shown in FIG. 2 and 4, the filler material 78 insulates all portions of the electrical components from the housing 12. The filler, which is placed in the housing 12 in a liquid state, is permitted to solidify to the extent that it will support the core and coil assembly 24 and the capacitor 26 and prevent them from sinking and engaging the base 14 of the housing 12. After the filler 78 has so solidified, the free ends of the leg portions 72 of the support members 68 are severed and removed to the greatest extent possible as is shown in FIG. 6.

Thereafter, the remainder of the housing 12 is filled with the same filler material 78, to completely fill the housing and thereby completely cover the electrical components including in the specific embodiment shown the core and coil assembly 24 and the capacitor 26 as is shown in FIG. 6. The assembly of the lamp ballast is completed by securing a cover 80 to the top of the housing 12 as shown in FIG. 5.

Summarizing,-FIGS. 3, 4, and 6 show three steps in the assembly of a lamp ballast in accordance with the method of this invention. FIG. 3 showing the support member 68 supporting the core and coil unit assembly 24 in a space relationship with respect to the casing before any filler material 78 is added. FIG. 4 shows the addition of filler material 78 to a first level, wherein the filler material is permitted to solidify to the extent necessary to support the core and coil assembly 24 such that the temporary suspension means may be removed. FIG. 6 shows the same cross-section of a completely assembled lamp entirely different configuration. In producing a lamp ballast in accordance with the method of this invention, what is required is that it be possible to suspend the core and coil assembly 12 in the housing 12 out of contact with the side walls, the end walls, and the base of the housing 12 while a suitable filler material 78 is added to a level wherein upon solidification it will support the core and coil assembly. Thereafter, that portion of the temporary suspension means which engaged the housing or extended therefrom thru the open top to support the core and coil assembly 24 is removed. When the housing 12 is completely filled with the filler material 78, the core and coil assembly is completely encased by the filler material 78. In a completely assembled lamp ballast no portion of the temporary suspension means extends through the filler material 78 from the core and coil assembly 24 to the housing 12.

While the novel and improved lamp ballast and method of producing the same in accordance with this invention, eliminated any contact between the core and coil assembly and the housing, and eliminates any suspension members extending therebetween, it can not of course eliminate the insulated leads extending from the core and coil assembly through the housing for external connections. However, the elimination of any contact between the core and coil assembly, or a member supporting it and the housing is of course desirable for the reasons previously set forth.

In order to minimize the possibility of moisture entering the core and coil unit by way of creepage along the insulated leads, the filler material and the insulation on the leads are chosen to provide maximum adhesion therebetween. Thus, while a lamp ballast constructed in accordance with the method of this invention does not eliminate the connecting leads extending from the core and coil assembly through the casing, it does eliminate all direct contacts and other members extending therebetween and thereby significantly improves the resistance of the lamp ballast to the entrance of moisture into the core and coil assembly.

In an alternate arrangement in accordance with this invention, some sort of temporary suspension means would be secured to an upper portion of the core and coil assembly as viewed in FIG. 2. After the filler material 78 is added to a level such as is shown in FIG. 2, and the filler material has solidified to support the core and coil assembly, the suspension means may be removed. For instance, a clamping device with sufficient clamping force to support the core and coil assembly might engage the outer edges of the outer legs 32 to support the core and coil assembly in the desired predetermined position in the housing 12. After sufi'icient filler material 78 has been added to the casing such that upon solidification it will support the core and coil assembly 24, and the filler material 78 has solidified, the supporting clamping device would be removed and the housing 12 completely filled with the filler material.

While in accordance with the patent statutes the preferred embodiment of this invention has been shown and described, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from this invention in its broader aspects and, therefore, it is intended that the appended claims cover all such changes and modifications a fall within the true spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A method of producing a lamp ballast having at least one magnetic core and coil assembly which is encased in a housing, said method comprising the steps of: suspending by a temporary suspension means said at least one magnetic core and coil assembly in said housing in a spaced relationship such that said at least one magnetic core and coil assembly does not contact said housing, partially filling said housing with a liquid filler material to a level such that upon hardening said magnetic core and coil is maintained in the spaced relationship; removing the suspending effect of said temporary suspension means, completely filling said housing with said filler material to completely encase said core and coil assembly in said housmg.

2. A method of producing a lamp ballast having at least one magnetic core and coil assembly which is encased in a housing, said method comprising the steps of: attaching temporary suspension means to said at least one magnetic core and coil assembly, suspending by engaging said temporary suspension means with said housing said at least one magnetic core and coil assembly in said housing in a spaced relationship such that said at least one magnetic core and coil assembly does not contact said housing, partially filling said housing with a liquid filler material to a level such that upon hardening said magnetic core and coil assembly is maintained in the spaced relationship, removing at least that portion of said temporary suspension means which engages said housing, completely filling said housing with said filler material to completely encase said core and coil assembly in said housing.

3. A method of producing a lamp ballast having at least one magnetic core and coil assembly which is encased in a housing, said method comprising the steps of: engaging said at least one magnetic core and coil assembly in the bight of at least one U-shaped support member which has a bight portion joining two leg portions and a hook portion formed at the free ends of said leg portions, suspending by engaging said hook portions of said at least one U-shaped support member with said housing, said at least one magnetic core and coil assembly in said housing in a spaced relationship such that said at least one magnetic core and coil assembly does not contact said housing, partially filling said housing with a liquid filler materi al to a level such that upon hardening said magnetic core and coil assembly is maintained in the spaced relationship, severing and removing at least said hook portions of said at least one U-shaped support member, completely filling said housing with said filler material to completely encase said core and coil assembly in said housing.

4. A lamp ballast having at least one magnetic core and coil assembly, a housing, and a hardenable filler material encasing said at least one magnetic core and coil assembly; formed by: suspending said at least one magnetic core and coil assembly in said housing in spaced relationship thereto by engaging said at least one magnetic core and coil assembly and said housing with temporary suspension means; partially filling said housing with said filler material to a level sufficient to support said at least one magnetic core and coil assembly in spaced relationship within said housing; removing said temporary suspension means from engagement with said housing; and substantially completely filling said housing with said hardenable filler material. 

1. A method of producing a lamp ballast having at least one magnetic core and coil assembly which is encased in a housing, said method comprising the steps of: suspending by a temporary suspension means said at least one magnetic core and coil assembly in said housing in a spaced relationship such that said at least one magnetic core and coil assembly does not contact said housing, partially filling said housing with a liquid filler material to a level such that upon hardening said magnetic core and coil is maintained in the spaced relationship; removing the suspending effect of said temporary suspension means, completely filling said housing with said filler material to completely encase said core and coil assembly in said housing.
 2. A method of producing a lamp ballast having at least one magnetic core and coil assembly which is encased in a housing, said method comprising the steps of: attaching temporary suspension means to said at least one magnetic core and coil assembly, suspending by engaging said temporary suspension means with said housing said at least one magnetic core and coil assembly in said housing in a spaced relationship such that said at least one magnetic core and coil assembly does not contact said housing, partially filling said housing with a liquid filler material to a level such that upon hardening said magnetic core and coil assembly is maintained in the spaced relationship, removing at least that portion of said temporary suspension means which engages said housing, completely filling said housing with said filler material to completely encase said core and coil assembly in said housing.
 3. A method of producing a lamp ballast having at least one magnetic core and coil assembly which is encased in a housing, said method comprising the steps of: engaging said at least one magnetic core and coil assembly in the bight of at least one U-shaped support member which has a bight portion joining two leg portions and a hook portion formed at the free ends of said leg portions, suspending by engaging said hook portions of said at least one U-shaped support member with said housing, said at least one magnetic core and coil assembly in said housing in a spaced relationship such that said at least one magnetic core and coil assembly does not contact said housing, partially filling said housing with a liquid filler material to a level such that upon hardening said magnetic core and coil assembly is maintained in the spaced relationship, severing and removing at least said hook portions of said at least one U-shaped support member, completely filling said housing with said filler material to completely encase said core and coil assembly in said housing.
 4. A lamp ballast having at least one magnetic core and coil assembly, a housing, and a hardenable filler material encasing said at least one magnetic core and coil assembly; formed by: suspending said at least one magnetic core and coil assembly in said housing in spaced relationship thereto by engaging said at least one magnetic core and coil assembly and said housing with temporary suspension means; partially filling said housing with said filler material to a level sufficient to support said at least one magnetic core and coil assembly in spaced relationship within said housing; removing said temporary suspension means from engagement with said housing; and substantially completely filling said housing with said hardenable filler material. 